OCR Text |
Show 1886.] GEOCOCCYX CALIFORNIANUS. 469 The spinal pterylosis is represented by two broad, longitudinal tracts well separated from each other in the middle line by a naked-skin area overlying the vertebral column. These spinal pterylae gradually converge towards each other as they approach the pelvic region, over which they merge into one feather-space, which becomes pointed behind and terminates just in front of the nude oil-gland. The upperside of the coccygeal protuberance is also sparsely feathered, being divided from a more generously covered area below by the line of horizontally arranged pits for the quill-butts of the rectrices of the tail. An exceedingly narrow tract, on either side, springs from the posterior margin of the outer bifurcation of the ventral tract just below the arm-pit, to run longitudinally down the side, in front of the thigh, to become lost before it arrives at the margin of the vent. This strip seems to be composed simply of a double row of feathers, and might appropriately be termed the lateral tract. The. patagium of the arm is very thinly feathered anteriorly, while its dorsal aspect is quite completely covered ; the remainder of the pterylosis of the pectoral limb presents us with nothing of a peculiar nature. The posterior marginal boundary of this " alar tract" is, as usual, terminated by the row of quill-butts of the primary feathers of the wing. Passing now to the crural region, we find a posterior limb but sparsely feathered, while a conspicuous " femoral tract " extends obliquely across the dorsal aspect of the thigh, and rapidly narrowing, runs along the pubic line, finally merging into the " caudal tract." Geococcyx shows its best-marked apteria in front, in the mesial space between the inner strips of the ventral tracts, and laterally to the outer side of the spinal pterylosis, where, indeed, for a considerable space no feathers may be said to occur at all. A well-marked dorso-longitudinal naked area is also to be seen. In this Ground-Cuckoo we notice a membrane, stretching between the thigh and leg, which corresponds to the patagial fold of the pectoral limb, and fully as well-developed. Before closing this part of our subject it is of interest to observe the general form of Geococcyx, which, now that its feathers have been removed, can be studied to the best advantage. It will be seen how perfectly its figure has come to assume a shape best adapted to the peculiar requirements of the bird. Its pelvic limbs are large, muscular, and consequently powerful, while the pectoral ones are decidedly less so, though by no means weak or inefficient. The body-form of this prince of avian racers is what almost might be called " clipper built," so admirably fashioned is it to the needs and ends of a rapid running bird of the size of our subject. With these few remarks upon the external organization and appearance of Geococcyx we will now close this part of our discussion, and pass to the consideration of some of the features presented in the structure of the remainder of its economy. |